High Sensitivity of HCl Gas Sensor Based on Pentacene Organic Field-Effect Transistor

The gas sensing properties were investigated for detecting various hydrochloric acid gas concentrations by fabricating the pentacene-based organic field-effect transistor (FET). The pentacene thin film was simply deposited by thermal evaporation process using a shadow mask. The source/drain electrode was formed on heavily boron doped silicon substrate in the form of interdigitated electrode pattern, which showed high gas reactivity by dense patterns between electrodes. The field-effect mobility, subthreshold slope, threshold voltage, on/off current ratio have been observed as 1.8 cm 2 /Vs, 0.64 V/dec, 5.6 V, 10 6 , respectively. We measured the change in the amount of drain current depending on the concentration of hydrochloric acid gas from 3 to 20 ppm. As a result, the amount of drain current increased as the concentration of hydrochloric acid gas increased. Additionally, at room temperature, we were able to observe the recovery time to its initial state about 200 s at hydrochloric acid gas concentration of 20 ppm. These pentacene-based organic FETs are expected to be able to detect various hazardous acid gases which are hardly detected by inorganic sensors due to corrosion problem in the form of arrays in the future.